One type of signal processing typically associated with high-density magnetic recording channels is the time-domain equalization. Such equalization is used to reshape a readback signal received by the channel to an approximation of a desired target waveform in the time domain, such as used in a Partial Response, Maximum Likelihood (PRML) detection read channel (see the paper "A PRML System for Digital Magnetic Recording" by R. D. Cidecian et al., IEEE Journal on Selected Areas in Communication, vol.10, no.1 January 1992). As will be recognized, reshaping the readback signal allows intersymbol interference (ISI) to be reduced and controlled, facilitating reliable sequential decoding of the digital information stored on disk.
Basic instrument for time-domain equalization in magnetic recording channels is the transversal equalizer, be it in a digital implementation (see U.S. Pat. No. 5,422,760, issued Jun. 6, 1995, entitled "Disk Drive Method Using Zoned Data Recording and PRML Sampling Data Detection with Digital Adaptive Equalization" filed Aug. 17, 1994 by Abbott et al.) or in analog implementation. The analog transversal equalizer, in turn, can be implemented either in discrete-time version, on samplers or in a continuous-time version. A continuous-time implementation is described in U.S. Pat. No. 5,592,340, issued Jan. 7, 1997, entitled "Communication Channel with Adaptive Analog Transversal Equalizer" filed Sep. 21, 1994 by Minuhin et al.
Transversal equalizers may be Finite Impulse Response (FIR) filtering devices or Infinite Impulse Response (IIR) filtering devices like the ones described in the above-identified Minuhin et al. '340 patent. A recent paper by V. Minuhin et al. "Adaptive, Analog, Continuous-Time Time-Domain Equalization for Sampled Channels in Digital Magnetic Recording" IEEE Transactions on Magnetics, September 1997, shows that IIR filters outperforms FIR filters not only as a practical device, but also theoretically.
The Minuhin et al. paper refers to the particular equalizer described as a Generalized Transversal Equalizer (GTE), to distinguish it from well known analog transversal equalizers. A need exists for an improved filtering system for a communication channel, and particularly for magnetic recording channel by making it simpler and more economical in manufacturing; reduce its size and power dissipation.
The present invention provides a solution to this and other problems, and offers other advantages over the prior art.